1. Field of the Invention
The invention relates to an image pick-up apparatus, more particularly to an image pick-up apparatus that can correct aberrations attributed to curvature-of-field characteristics of an object lens thereof.
2. Description of the Related Art
Referring to FIG. 1, a conventional image pick-up apparatus 1 found in digital still cameras or video cameras including an object lens 11 and an image-sensing device 12 is shown. The object lens 11 includes at least one lens element with a predetermined curvature and serves to project an image 111 of an object 100 to be picked-up. The image-sensing device 12 has a planar image-receiving side 121 disposed to receive the image 111 projected by the object lens 11, and includes an image-sensing unit 122. In general, the image-sensing device 12 is either a charge-coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) sensor.
In view of curvature-of-field characteristics of the object lens 11, the object lens 11 introduces aberrations and distortions into the image 111 that is projected to the planar image-receiving side 121 of the image-sensing device 12. As a result, during focus adjustment, the image output of the apparatus 1 may exhibit a clear central part with slightly blurred edge parts, or clear edge parts with a slightly blurred central part.
While it is possible to modify the construction of the object lens to minimize aberrations and distortions in the image projected thereby, the modified object lens would be bulky and thus unsuitable for portable applications.
FIG. 2 illustrates an image pick-up apparatus according to U.S. Pat. No. 4,467,361. In the apparatus of FIG. 2, the image receiving side 121′ of the image-sensing device 12′ is formed with a predetermined curvature to match the curvature-of-field characteristics of the object lens 11′. As a result, aberrations and distortions introduced by the object lens 11′ into the image 111′ can be corrected accordingly. However, fabrication of the curved image receiving side 121′ of the image-sensing device 12′ that matches the curvature-of-field characteristics of the object lens 11′ is difficult and costly to be implemented.